All power generating systems such as diesel or gas power generators, wind turbines, vehicle and motors etc., have a starting torque. For example, wind turbines have a start and stop speed and a cut-in wind speed.
The two common methods of capturing wind power are Horizontal Axis Wind Turbines (HAWT) or Vertical Axis Wind Turbines (VAWT). VAWT using lift-type turbine blades. This technology has been studied and analyzed using the Darrieus turbine since the mid-1930. The technology has been well understood and researched extensively by NASA and other research institutions. Today, lift type VAWTs are commonly available, the dominant suppliers being from China.
Some of these VAWT wind turbines may stop in a position such that restarting them would require higher wind velocities. This is particularly noted with Darrieus wind turbines. There is a lot of prior art on what can be used to self-start a Darrieus wind turbine. One method of self-starting Darrieus wind turbine is disclosed in Garby et al. (US2011/0031756). Garby et al. describes using magnetic bearings that can use used to create an axial lift that reduces the axial load on the bearings, which in turn reduces the starting torque. Noteworthy in the description in this reference are the benefits of reduced torque and is shown by FIG. 10 through FIG. 12. In this invention electrical power is applied to the bearings creating a magnetic force to overcome the starting torque issue.
Another method described by Latos et al. (U.S. Pat. No. 5,512,811) is to convert electrical energy to mechanical energy to start a turbine engine. Once started, the electronics described in the invention shows how the mechanical energy can be converted back to electrical energy and stored.
Gupta et al. (U.S. Pat. No. 6,911,742) describes a gas driven turbine and a permanent magnet alternator rotating on a common shaft. A control circuit during a startup mode switches the inverter circuit to the starter to wind down the alternator and during the power-out mode switches to the inverter circuit. Gupta et al. also describes in (U.S. Pat. No. 6,605,928) how the alternator functions as a motor to raise the speed of the turbine at a safe ignition speed.
Bhargava et al. (U.S. Pat. No. 6,323,625) describes a similar method as Gupta et al. however, spins the turbine up to a safe speed. It is shown how the embedded electronics provides power through the AC output circuit for this function.
The idle windmills do not provide consistent power supply and reliable energy source to the grid or other energy consumers. Inconsistency in supply of power is detrimental for the users and utility companies of wind turbines or motors as a source of alternate energy. There is need to harness wind energy and provide reliable consistent power supply to the grid.